It is a goal of model railroaders to build and run model railroad rolling stock which is as close to that used in prototype railway rolling stock as is possible. To this end, a great deal of effort is expended in order to duplicate, in scale, all of the features of prototypical rolling stock. In the case of couplers for prototypical rolling stock, as are used in the western hemisphere, couplers are made with a coupler head, attached to a shank, which is in turn connected to the rolling stock by means of a draft box. Attached to the coupler head is a knuckle which engages a like knuckle on another unit of rolling stock. Such structures are present on both prototypical railway and some model railroad couplers, however, the couplers that have been in use on model railroads deviate to a greater or lesser degree, depending on manufacturer, from the prototypical in order to accommodate the much smaller scale of the coupler components.
Another desirable feature of a model railroad coupler is the ability to remotely uncouple units of rolling stock from one another without physically handling the units of rolling stock. One form of remote uncoupling involves the use of a coupler, which is made of a non-magnetic material, with a simulated air hose, which is made from a magnetically-active metal, and which, when subjected to a magnetic field, may be caused to swing, shifting the coupler knuckle into an open position, when the simulated air hose is positioned over a magnetic ramp, whether such ramp be a permanent magnet or an electromagnet. A number of such magnetically actuated model railroad uncouplers are disclosed in patents to Edwards et al., such as U.S. Pat. Nos. 3,111,229, 3,115,255, 3,117,676, 3,469,713, 3,564,766, and 3,942,648. Variations on the magnetic couplers of Edwards et al. are depicted in U.S. Pat. No. 5,785,192 to Dunham et al., the full disclosure of which is incorporated herein by reference, U.S. Pat. No. 4,335,820 to Gramera, U.S. Pat. No. D326,693, also to Gramera, and U.S. Pat. No. 5,509,546 to Staat. Another for of remote uncoupling involves linking a coupler to a remote uncoupling actuator, which is an electromechanical device, which is remotely triggered, e.g., by DCC. Although some units of model railroad rolling stock may be equipped with a remote uncoupler actuator, it is desirable to have all couplers capable of magnetically actuated uncoupling.
The forgoing references are all magnetically actuated, however, problems arise when (1) only one coupler is mechanically (vice mechanically) actuated, as by a remote uncoupling operation, wherein only one coupler knuckle may open, resulting in “jamming,” or locking of the two couplers together, prevent uncoupling; and (2) in the case of travel over a magnetic uncoupling ramp, a well known device to those of ordinary skill in the art, prior to “delayed uncoupling”, i.e., positioning the coupler knuckles in an uncoupled position and then backing the train to the location where the train is to be split, travel over an uncoupling ramp may result in the lead coupler pulling the trailing coupler off center, which may prevent the coupler knuckle on the trailing coupler from uncoupling and preventing the necessary relative swinging of the couplers for delayed uncoupling.